The invention relates to a packaged capacitor, particularly a packaged hybrid capacitor including a valve metal anode and a pseudocapacitor cathode, sealed within a metal container and having a button shape, that is easily and economically manufactured.
Hybrid capacitors are well-known through commonly assigned U.S. patents, for example, U.S. Pat. Nos. 5,369,547, 5,469,325, 5,559,667, 5,754,394, 5,737,181, 5,754,394 and 5,982,609, the contents of which are incorporated herein by reference. These capacitors are referred to as hybrid capacitors because they include an anode of an oxidized valve metal as in, for example, conventional wet slug electrolytic capacitors. Examples of such valve metals which form native oxides include tantalum, niobium, aluminum, and zirconium. Typically, these wet slug capacitors anodes are made by sintering so that a porous anode with an oxide coating is prepared as the capacitor anode. The anode may be a pellet or other self-supporting body, or may be a coating on an electrically conducting support. The wet slug capacitor anode provides an advantage, both in the wet slug capacitor and in the hybrid capacitor, of a relatively high breakdown voltage.
In hybrid capacitors, the cathode is a porous metal oxide film typically used in pseudocapacitors in order to provide a relatively large capacitance. Examples of such metals having at least two stable oxidation states in the electrolyte used in the hybrid capacitor include ruthenium, iridium, nickel, rhodium, platinum, palladium, and osmium. Of these metals, perhaps ruthenium is the most preferred for forming the oxide layer cathode of the hybrid capacitor. Because of the way the voltage applied across a hybrid capacitor divides across the anode and the cathode, the relatively high breakdown voltage of the wet slug capacitor is achieved with the relatively high capacitance provided by a pseudocapacitor.
Hybrid capacitors of various configurations are described in the U.S. patents mentioned above. These capacitors can be manufactured in various sizes and shapes, although the configurations are not always handy for particular installations. Accordingly, it is an objective of the present invention to provide a packaged hybrid capacitor that is compact, easy and economical to manufacture, and that can be easily installed in available space, including on a printed circuit board.
A packaged hybrid capacitor according to an aspect of the invention includes a metal cup having a bottom wall with a periphery and an upstanding sidewall at the periphery and surrounding the bottom wall; a first capacitor electrode located within the sidewall and on the bottom wall of the metal cup; an endless electrically insulating plastic sealing member having a base and an outer wall upstanding from the base, disposed within the metal cup, the outer wall having a shape and size fitting within the cup, adjacent the sidewall of the cup; a metal cover including a top wall and a peripheral skirt extending from and surrounding the top wall and inclined relative the top wall toward an inside surface of the metal cover; a second capacitor electrode on the inside surface of the top wall; a separator disposed between the first and second electrodes; and an electrolyte within the capacitor and in contact with the first and second capacitor electrodes, wherein the sidewall of the metal cup bears against the peripheral skirt, with the outer wall of the sealing member interposed between the sidewall and the peripheral skirt, sealing the packaged hybrid capacitor and electrically insulating the metal cup from the metal cover.
The sealing member employed in sealing the capacitor preferably has, in crosssection, a channel shape including a inner wall opposite the outer wall. The sealing member is preferably selected from the group consisting of polytetrafluoroethylene, polyethylene, polypropylene, silicone rubber, natural and synthetic rubbers, elastomers, polyvinyl chloride, and a moldable elastomer-polymer blend.